The present invention relates to semiconductor memory devices and refresh methods thereof, and more particularly, to semiconductor memory devices with reduced self-refresh power consumption and refresh methods thereof.
Some mobile electronic products, such as smart phones, require large-capacity dynamic random access memory (DRAM). Generally, in semiconductor memory devices such as DRAM, data stored in a memory cell may be changed due to leakage current. Accordingly, a refresh operation is required to periodically recharge the data stored in the memory cell. However, when a refresh operation is performed in DRAM in a device that is in standby mode, undesirable power consumption may occur.
To overcome the problem, a method of controlling a refresh operation in units of memory banks has been suggested. This method has been suggested to reduce power consumption by moving data that is scattered in various memory banks of a DRAM to a single memory bank and omitting to refresh empty memory banks.
However, the method requires power and time for movement of data between memory banks and has inefficiency in granularity since each memory bank is controlled independently. Additionally, it is desired to reduce power consumption caused by a refresh operation in DRAM in order to use DRAM.